1. Field of the Invention
The present invention relates to a method and an apparatus for producing a plastic cylinder head cover, and more particularly to a method and an apparatus for producing a plastic cylinder head cover that can prevent deformation of a hole in an oil control valve holder during insert molding.
Another aspect of the present invention relates to a method and an apparatus for producing a plastic cylinder head cover, and more particularly to a method and an apparatus for producing a plastic cylinder head cover that can prevent deformation of a hole in an oil control valve holder during insert molding, as well as prevent scratches and deformation of a mounting surface of the oil control valve holder.
2. Description of Related Art
Conventionally, a cylinder head cover for internal combustion engines is commonly known, which has a metallic oil control valve (hereinafter also referred to in abbreviation as “OCV”) holder for attaching an OCV retrofitted with bolts to a cover body. This OCV holder is typically formed with a hole for attaching an OCV and communication passages for connecting oil passages in the OCV with oil passages or the like on the side of the cylinder head. The problem with this cylinder head cover is that, because the OCV holder is retrofitted, the number of production man-hours is large and the production cost is high.
Therefore, as a cylinder head cover that solves the above problem, a plastic cylinder head cover having an OCV holder as an integral part thereof by insert molding has been proposed (see, for example, Japanese Laid-Open Patent Application Publication (JP-A) Nos. 2006-316640 and 2007-107479). JP-A-2006-316640 discloses plugging both of the open axial ends of the hole of the OCV holder during insert molding (see JP-A-2006-316640, paragraph [0043] and FIG. 6). This prevents plastic material from entering the hole of the OCV holder.
The above JP-A-2007-107479 discloses an OCV holder having a mounting surface on which it is mounted to the cylinder head, a hole oriented along an axis inclined to a plane direction of this mounting surface, and two faces containing open ends of this hole (see JP-A-2007-107479, FIG. 6). During insert molding of this OCV holder, one of the two faces which has a larger area is subjected to a relatively large pressure from the plastic material. In some cases, for example, this may cause deformation of a lower corner of the OCV holder 103 as indicated by an imaginary line in FIG. 11, leading to deformation of the hole 107 (see, for example, FIG. 12B). Such deformation of the hole of the OCV holder may cause oil leakage between the OCV holder and the OCV during use of the cylinder head cover. Accordingly, in the above JP-A-2007-107479, the OCV holder is set such that its mounting surface is entirely abutted against a lower mold during insert molding so as to prevent deformation of the hole of the OCV holder (see JP-A-2007-107479, FIGS. 13 and 14).
However, with the plastic cylinder head cover disclosed in the above JPA-2006-316640, a middle part of the hole of the OCV holder remains hollow during insert molding. Because of this, the hole 107 of the OCV holder 103 may sometimes deform by the plastic material filling pressure during the molding and contraction after the molding, for example as shown in FIGS. 11 and 12. Such deformation of the hole 107 of the OCV holder 103 may cause oil leakage between the OCV holder and the OCV during use of the cylinder head cover.
It is difficult to enhance the dimensional accuracy of both the hole and the mounting surface of the OCV holder relative to the cover body of the cylinder head cover. It is therefore the practice, for example, to enhance the dimensional accuracy of the hole relative to the cover body while the dimensional accuracy of the mounting surface is lowered. In this case, with the plastic cylinder head cover disclosed in the above JP-A-2007-107479, because the mounting surface of the OCV holder is entirely abutted against the lower mold, the mounting surface of the OCV holder is susceptible to scratches and to deformation due to excessive pressure exerted thereto. This may result in oil leakage between the OCV holder and the cylinder head during use of the cylinder head cover.